1. The Field of the Invention
The present invention relates to mixing blocks and, more specifically, mixing blocks used in systems for mixing and suspending sterile and non-sterile fluids.
2. Present State of the Art
In the chemical industry, and in particular the pharmaceutical industry, there is a need for a system capable of holding liquids and mixtures of liquids and solids where a sterile environment can be maintained while providing means for stirring, mixing, resuspending, sampling, and complete delivery of the contents. To date, the industry has relied upon stainless steel storage vessels with associated stirring devices, ports, and mixers. These associated pieces of equipment require special seals in order to assure that the sterile conditions established within the device are maintained during mixing and pumping.
Due to the weight of these stainless steel devices, they are difficult to maneuver, which leads to increased production time. These stainless steel systems often require special handling equipment. When these stainless steel devices are used to transport bulk product, significantly higher shipping costs result due to the weight of the container and the added cost of returning the empty system for future use.
Stainless steel systems are expensive to build and thus impractical for single use disposal. As a result, conventional stainless steel systems must be cleaned and re-sterilized for reuse. This process may involve chemical cleaning with agents such as perchlorate solution, and the attendant disposal problems associated with disposal of such cleaning chemicals. After cleaning, the systems must be inspected and tested to assure that all foreign matter has been removed. Since new products will be introduced, validation of the cleaning and re-sterilization procedures as well as tests to assure efficacy must be completed. This also adds to the costs and complication of using the stainless steel systems.
Since the stainless steel systems are expensive, it is not cost effective to maintain several different sizes of the vessels. As a result, vessel size is usually set to the largest expected batch of material. When small batches are prepared, they are stored in oversized containers with the attendant costs and problems which have been previously described.
One of the primary uses for this type of vessel is the storage and transportation of sterile suspensions of alum in an aqueous medium for use in the production of vaccines. In practice, a sterile alum suspension is prepared in the vessel and shipped to the area where inoculation with the bulk virus or bacteria stock will occur. Since the suspension may be prepared well in advance of inoculation, the system must also serve as a storage container.
Prior to inoculation, the alum must often be resuspended. In many instances, uniform particle size and the preparation of a homogeneous suspension of the alum are critical to the success of the final product. Once resuspension has been assured, the suspension may be pumped into a vessel from which inoculation will occur or inoculation may be carried out from the storage container.
Resuspension of solutions stored in stainless steel systems is often accomplished by shaking the containers using specialized equipment such as paint shaking type devices. Such equipment is often unaccessible, especially in remote areas, and can be very inconvenient, particularly for large containers. In the alternative, the solution can be cycled into and out of the container until the solution becomes homogeneous. This cycling process, however, takes a relatively long time and, depending on the size of the container and type of solution, cannot guarantee that the solution is homogeneous throughout the container.